An extrusion coating method, an extrusion coating machine, and its working method

Abstract

This invention provides an extrusion coating method, an extrusion coating machine, and a working method. When coating the active material slurry, the method avoids coating the areas where electrode tabs need to be welded, leaving neat blank spaces, thereby directly eliminating the need for powder removal from the source. The method is as follows: for areas on the current collector requiring normal coating, a complete coating area is applied; for areas on the current collector where the electrode tab welding positions are located, a blank zone is left, and then the blank zone is coated in sections. Slurry is applied to areas where electrode tabs do not need to be welded, while blank spaces are left at the areas where electrode tabs need to be welded as electrode tab welding positions.

Description

Technical Field

[0001] This invention relates to a coating method and a coating machine, belonging to the field of extrusion coating technology. Background Technology

[0002] During the production of battery electrodes, a blank area without active material is usually left at the end of the electrode for welding tabs. The coating process involves uniformly coating the positive or negative electrode slurry onto the positive or negative current collector, leaving a blank area on the current collector, which is the tab welding groove.

[0003] Current coating processes often employ laser cleaning to create the tab welding slots. The laser cleaning process involves first fully coating the current collector (copper or aluminum foil) with an active material slurry to form a complete coating; then, a laser removes the coating at the tab location. This method requires pre-reserved locations for welding the tabs, which are then scanned with a high-energy laser to vaporize and remove the surface active material coating, exposing the underlying metal current collector.

[0004] Laser cleaning has the following disadvantages: High equipment cost: requires a high-precision laser system; Cleaning issues: laser ablation generates dust (active material and conductive agent particles), which may contaminate the electrode or the inside of the battery; Damage risk: improper laser energy control may damage the current collector substrate and affect the electrode tab welding strength; Consistency challenge: it is difficult to control the uniformity of the width and depth of the powder cleaning. Summary of the Invention

[0005] In view of this, the present invention provides an extrusion coating method, which adopts a method in which the position where the electrode tabs need to be welded is not coated when coating the active material slurry, and a regular blank grid is left directly, thereby avoiding the need for powder cleaning from the source.

[0006] The technical solution of the present invention is as follows: an extrusion coating method, wherein for the area on the current collector that requires normal coating, the normal material area is coated in a complete coating manner; for the area on the current collector where the electrode tab welding position is located, a blank band is left, and then the blank band is coated in a partitioned manner, where the position where the electrode tab does not need to be welded is filled with slurry, and the position where the electrode tab needs to be welded is left with blank grids as electrode tab welding positions.

[0007] As a preferred embodiment of the present invention, while leaving blank areas, the blank areas are simultaneously coated and left blank, thereby completing the normal coating process in one coating process and obtaining the electrode tab welding position of the blank grid.

[0008] The present invention also provides an extrusion coating machine, comprising: a double-layer die head, an upper gasket, and a lower gasket; the double-layer die head includes an upper die head and a lower die head, the upper die head and the lower die head having independent internal cavities for filling slurry; The outer surface of the upper die head is provided with an upper feed port that communicates with its internal cavity, and the outer surface of the lower die head is provided with a lower feed port that communicates with its internal cavity. The double-layer die head is provided with a coating port shared by the upper and lower die heads; The upper gasket is horizontally positioned at the bottom of the upper die head, and the lower gasket is inclinedly positioned inside the lower die head, such that one end of the upper gasket and one end of the lower gasket are both located at the coating port. The slurry in the upper and lower mold heads can be independently controlled to start and stop the conveying process; The upper gasket is used to coat the normal material area on the current collector, and to leave a blank band by controlling the start and stop of the slurry delivery in the upper die head; The lower pad and lower die head work together to fill the material discharge area in the blank area where no electrode tabs need to be welded, and block the material area in the area where electrode tabs need to be welded, leaving blank grids for welding electrode tabs.

[0009] In a preferred embodiment of the present invention, the upper gasket has a strip groove, with the end of the strip groove facing the coating port.

[0010] In a preferred embodiment of the present invention, the lower gasket has a groove corresponding to the area of ​​the strip groove, and the groove has a plurality of spaced baffles extending in the front-back direction, the baffles corresponding to the positions on the current collector where the electrode tabs need to be welded; the area between adjacent baffles is a material replenishment area.

[0011] Furthermore, the present invention also provides a method for operating the above-mentioned extrusion coating machine: Material feeding and filling: The slurry is pumped into the upper and lower mold heads respectively through the feeding system; Coating process: The current collector passes through the coating port at a uniform speed, closely following the back roller. For the normal coating area, the upper die head starts slurry delivery. Under pressure, the slurry in the upper die head flows out of the coating port through the strip groove on the upper pad, coating the normal material area on the current collector. For the area where the electrode tab is to be welded, the upper die head stops slurry delivery, and the lower die head starts slurry delivery. The replenishment area on the lower pad allows slurry to pass through, and replenishment is performed in the blank zone. The baffle prevents slurry from flowing out at this point, leaving blank spaces for welding the electrode tab.

[0012] Beneficial effects: (1) The extrusion coating method of the present invention adopts the method of not coating the position where the electrode tab needs to be welded when coating the active material slurry, and directly leaving a regular blank grid. This can eliminate the laser process, directly avoid the need for powder cleaning from the source, and save expensive laser equipment and its operation and maintenance costs. In addition, since there is no need to use laser ablation, there is naturally no dust generated by this process, which improves the cleanliness of production and battery safety.

[0013] (2) The coating method of the present invention can improve quality and consistency: the shape and size of the blank are directly determined by the coating process, the edges are neat, the surface of the current collector is intact, which is more conducive to subsequent ultrasonic welding and can improve welding reliability and consistency.

[0014] (3) The coating method of the present invention can improve efficiency: reduce production steps and increase the overall production line speed. Attached Figure Description

[0015] Figure 1 A schematic diagram showing the process of coating the current collector with the normal material area while leaving a blank band after skipping the gap; Figure 2 This is a schematic diagram showing the result of "touch-up" and "leave blank" within the blank area.

[0016] Figure 3 This is a schematic diagram of the overall structure of the coating machine; Figure 4 This is a schematic diagram of the upper gasket structure; Figure 5 This is a schematic diagram of the lower gasket structure; Figure 6 This is a product model diagram of the coating machine in Example 2.

[0017] Wherein: 1-upper gasket, 11-strip groove, 2-lower gasket, 21-replenishing area, 22-stop bar, 3-upper die head, 31-upper feed port, 4-lower die head, 41-lower feed port, 5-coating port, 6-current collector, 7-electrode tab welding position. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0019] Example 1: This embodiment provides an extrusion coating method that allows for the absence of coating on the areas where electrode tabs need to be welded when coating the active material slurry (i.e., coating material), leaving neat blank spaces for welding electrode tabs.

[0020] The coating method is as follows: For areas of the current collector (copper foil or aluminum foil) that require normal coating, apply the coating completely to create the normal material area; for areas where the current collector's tabs are welded, leave a blank zone and then apply the coating in sections. At locations where no tabs need to be welded, apply the slurry to create a material area, and leave blank squares for welding the tabs at locations where tabs need to be welded.

[0021] For example: First, while applying the normal material area to the current collector, leave a blank area by skipping gaps; that is, when applying the coating to the current collector, leave a blank area at intervals along its moving direction as a blank band; the blank band is the area where the electrode lug welding position of the current collector is located. Figure 1 As shown. The shape and size of the blank area (i.e., the blank band) are directly determined by the coating process based on the required size of the tab welding position; the "skip gap" can be equal or unequal intervals, depending on the actual tab welding position of the product.

[0022] As an example, by controlling the start and stop of the slurry delivery of the coating machine, a blank area is formed at the set position of the collector (i.e., the area where the electrode welding position is located); that is, the coating machine is controlled to deliver slurry in the normal coating area, and the coating machine is controlled to stop delivering slurry in the set blank area, thereby forming a blank band.

[0023] Then, "touch-up coating" and "blank space" are performed within the blank strip. Specifically, along the width of the coating strip, areas where welding tabs are not required are simultaneously coated with paste to form material zones, while blank squares are left at the locations where welding tabs are needed. This leaves several small, uncoated blank squares between the thin strips of paste created along the width of the coating strip. These small blank squares are the final tab welding positions 7. This achieves a high-precision "small square" blank pattern on the current collector, as shown in the image. Figure 2 As shown.

[0024] As an example: while forming the entire blank strip, it is "touched" and "left blank", so that the coating can be completed in one coating process and the electrode welding position 7 can be obtained at the same time.

[0025] This coating method can directly obtain regular blank grids (i.e., electrode tab welding positions 7) on the current collector, which are used for welding the electrode tabs. The precisely reserved welding points can ensure that the electrode tab welding is firm and reliable.

[0026] This coating method eliminates the need for additional powder removal equipment (which costs 5-10 million RMB) and also improves upon the problems of incomplete powder removal and excessive dust accumulation associated with laser powder removal. Example 2: Based on the extrusion coating method of Embodiment 1 above, this embodiment provides an extrusion coating machine capable of implementing the coating method.

[0027] like Figure 3 and Figure 6As shown, the extrusion coating machine includes: a double-layer die head, an upper gasket 1 and a lower gasket 2; the double-layer die head includes an upper die head 3 and a lower die head 4, the upper die head 3 and the lower die head 4 having independent internal cavities for filling slurry; the outer surface of the upper die head 3 is provided with an upper feed port 31 that communicates with its internal cavity, and the outer surface of the lower die head 4 is provided with a lower feed port 41 that communicates with its internal cavity (i.e., the upper die head 3 and the lower die head 4 feed in and out separately).

[0028] A coating port 5 is provided on the surface of the double-layer die head opposite to the upper feed port 31 and the lower feed port 41; the coating port 5 is the outflow channel of the slurry; the coating port 5 is located at the joint of the upper die head 3 and the lower die head 4, that is, the upper die head 3 and the lower die head 4 share a coating port 5; thus, the upper gasket 1 is horizontally set at the bottom of the upper die head 3, and the lower gasket 2 is inclinedly set inside the lower die head 4, so that one end of the upper gasket 1 and one end of the lower gasket 2 are both located at the coating port 5.

[0029] The slurry in the upper die head 3 and the lower die head 4 can be independently controlled to start and stop the conveying.

[0030] The upper gasket 1 is used to coat the normal material area on the collector 6, and by controlling the start and stop of the slurry delivery in the upper die head 3, a blank area is left by skipping gaps. Figure 4 As shown, the upper gasket 1 has a strip groove 11, with the end of the strip groove 11 facing the coating port 5. When the slurry conveying in the upper die head 3 is started, the slurry in the upper die head 3 flows out from the coating port 5 through the strip groove 11 on the upper gasket 1, thereby coating a normal material area on the collector 6. When the slurry conveying in the upper die head 3 is stopped (at which time the collector 6 is pushed forward normally), a blank area is left on the collector 6 as a blank band. Thus, by controlling the upper gasket 1 and the start and stop of the slurry conveying in the upper die head 3, a blank area can be left with gaps while coating a normal material area.

[0031] The lower gasket 2 and the lower die head 4 work together to "re-coat" and "leave blank" within the blank strip being manufactured. That is, the material outlet area is simultaneously coated in the blank strip where the electrode tabs do not need to be welded, while the material area is blocked in the blank strip where the electrode tabs need to be welded, leaving blank squares for welding the electrode tabs.

[0032] like Figure 5 As shown, the lower pad 2 also has a groove in the area corresponding to the strip groove 11 (the end of the groove 11 faces the coating port 5). The groove has several baffles 22 that are spaced apart and extend in the front-back direction. The baffles 22 correspond to the positions on the current collector 6 where the electrode tabs need to be welded. The area between adjacent baffles 22 is the replenishment area 21, so that the lower pad 2 can be used to replenish the coating and cover the blank area.

[0033] The working principle of the lower gasket 2 is as follows: It can be understood that the area on the lower gasket 2 corresponding to the strip groove 11 has a raised block (stop bar 22) and a recessed flow channel (filling area 21); when the upper die head 3 stops conveying slurry (at this time, a blank band appears on the current collector), the lower die head 4 starts conveying slurry. Thus, by utilizing the structure of the lower gasket 2, the section in the blank band that does not need to be welded with electrode tabs has a recessed slender flow channel as the filling area 21, allowing the slurry to pass through, thereby "filling in" several narrow, discontinuous material areas in the blank band to connect the normal material areas on both sides, enhance the structural strength of the electrode, and prevent large blank areas from causing the coating to crack and fall off during drying or rolling. In the blank area, where the electrode tabs need to be welded precisely, the lower pad 2 has a raised baffle 22 to prevent the slurry from flowing out at this point. As a result, several small square blank foils with no coating are left between the thin strips of material that have been applied, which serve as the final electrode tab welding positions 7. This achieves a high-precision "small square" blank pattern.

[0034] Therefore, it can be seen that the coating machine with this structural form controls the start and stop of the slurry delivery through the upper gasket 1 and the upper die head 3 to coat the normal material area and the entire blank area at the tab position (the upper die head 3 adopts an intermittent coating method). Controlling the start and stop of the slurry delivery through the lower gasket 2 and the lower die head 4, it simultaneously coats several material areas in the blank area where tab welding is not required, while leaving several small square foil positions at the tab welding positions through material blocking (the lower die head 4 adopts a zoned coating method). Thus, through a single coating process, an optimized electrode sheet is directly obtained on the current collector 6; the precisely reserved welding points ensure a firm and reliable tab welding.

[0035] The working process of this coating machine is as follows: Material feeding and filling: The slurry is pumped into the upper die head 3 and the lower die head 4 through the feeding system; Coating process: The current collector 6 passes through the coating port 5 at a constant speed, closely following the back roller. For the normal coating area, the upper die head 3 starts the slurry delivery. Under pressure, the slurry in the upper die head 3 flows out of the coating port 5 through the strip groove 11 on the upper pad 1, thus coating the normal material area on the current collector 6. For areas that need to be left blank, the upper die head 3 stops the slurry delivery, and the lower die head 4 starts the slurry delivery. Utilizing the structure of the lower pad 2, in the blank area where the electrode tabs do not need to be welded, the replenishment area 21 allows the slurry to pass through, "re-coating" several narrow, discontinuous material areas in the blank area. The baffle 22 prevents the slurry from flowing out at this point, thus leaving "small square" blanks between the replenished thin material areas as electrode tab welding positions 7.

[0036] The current collector 6 coated with a wet film enters a drying oven (such as an oven) for curing or drying, ultimately forming a uniform coating with controllable thickness.

[0037] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for extrusion coating, characterized in that, For areas on the current collector that require normal coating, apply the normal coating area using a full coating method; for areas on the current collector where the electrode tab welding position is located, leave a blank zone, and then apply the blank zone in a partitioned coating method. Apply slurry to the areas where the electrode tab does not need to be welded, and leave blank grids for the electrode tab welding positions at the areas where the electrode tab needs to be welded.

2. The extrusion coating method as described in claim 1, characterized in that, While leaving blank areas, the blank areas are filled with coating and left blank, thus completing the normal coating process in one coating process and obtaining the electrode tab welding position of the blank grid.

3. An extrusion coating machine, characterized in that, include: Double-layer die head, upper gasket (1) and lower gasket (2); the double-layer die head includes an upper die head (3) and a lower die head (4), the upper die head (3) and the lower die head (4) having independent internal cavities for filling slurry; The outer surface of the upper die head (3) is provided with an upper feed port (31) that connects to its internal cavity, and the outer surface of the lower die head (4) is provided with a lower feed port (41) that connects to its internal cavity. The double-layer die head is provided with a coating port (5) shared by the upper die head (3) and the lower die head (4); The upper pad (1) is horizontally positioned at the bottom of the upper die head (3), and the lower pad (2) is inclinedly positioned inside the lower die head (4), so that one end of the upper pad (1) and one end of the lower pad (2) are both located at the coating port (5). The slurry in the upper die head (3) and the lower die head (4) can be independently controlled to start and stop the conveying; The upper gasket (1) is used to coat the normal material area on the collector (6) and to leave a blank band by controlling the start and stop of the slurry conveying in the upper die head (3); The lower pad (2) and the lower die head (4) are used to fill the material discharge area in the blank area where the electrode tabs do not need to be welded, and to block the material area in the area where the electrode tabs need to be welded, leaving blank grids for welding the electrode tabs.

4. The extrusion coating machine as described in claim 3, characterized in that, The upper pad (1) has a strip groove (11), and the end of the strip groove (11) faces the coating port (5).

5. The extrusion coating machine as described in claim 4, characterized in that, The lower pad (2) has a groove corresponding to the area of ​​the strip groove (11). The groove has a number of spaced baffles (22) extending in the front-back direction. The baffles (22) correspond to the positions on the current collector (6) where the electrode tabs need to be welded. The area between adjacent baffles (22) is the material replenishment area (21).

6. The working method of the extrusion coating machine, characterized in that, The extrusion coating machine is the extrusion coating machine according to claim 5: Material feeding and filling: The slurry is pumped into the upper die head (3) and the lower die head (4) respectively through the feeding system; Coating implementation: The current collector (6) passes through the coating port (5) at a constant speed under the support of the back roller; for the normal coating area, the upper die head (3) starts the slurry delivery, and under pressure, the slurry in the upper die head (3) flows out from the coating port (5) through the strip groove (11) on the upper pad (1) and coats the normal material area on the current collector (6); for the area where the electrode tab welding position is located, the upper die head (3) stops the slurry delivery, the lower die head (4) starts the slurry delivery, the replenishment area (21) on the lower pad (2) allows the slurry to pass through, and replenishment is carried out in the blank area. The baffle (22) blocks the slurry from flowing out here, leaving a blank grid for welding the electrode tab.

Images